In the related art, an oil supply structure of an internal combustion engine provided with an oil flowing path formed above a camshaft, is known (for example, refer to JP 2007-127014A (reference 1))
Reference 1 discloses a lubricating oil supply structure (an oil supply structure of an internal combustion engine) which forms an oil flow-path (oil flowing path) inside thereof by bonding resin members to each other that extend along a camshaft of the internal combustion engine, and which includes a plurality of oil ejection holes which are opened toward a camshaft in a bottom portion of the oil flow-path. In the lubricating oil supply structure described in Reference 1, oil (engine oil) flows in the elongated oil flow-path from an oil supply hole provided in one end portion, is supplied to the other end portion opposite to the oil supply hole, and is ejected toward the camshaft from the oil ejection holes disposed in a shape of a row along the oil flow-path.
However, in the oil supply structure of the internal combustion engine described in Reference 1, in the elongated oil flow-path, it is considered that ejection pressure (ejection amount) of the oil varies due to a pressure loss in the oil flow-path, in the oil ejection hole which is close to the oil supply hole provided in one end portion and the oil ejection hole on the other end portion side far from the oil supply hole. Therefore, since it is necessary to supply a larger amount of oil to the oil flow-path in order to ensure the minimum necessary ejection amount in the oil ejection hole on the other end portion side, and there is a problem that the size of an oil pump which becomes a supply source of the oil increases to that extent.